Floating hot-melt extruded tablets for gastroretentive controlled drug release system

The purpose of this study was to investigate the influence of sodium bicarbonate on the physicochemical properties of controlled release hot-melt extruded (HW) tablets containing Eudragit((R)) RS PO and/or Eudragit((R)) E PO. Acetohydroxamic acid and chlorpheniramine maleate were used as model drugs. Sodium bicarbonate was incorporated into the tablet formulations and the drug release properties and buoyancy in media for HME tablets and directly compressed (DC) tablets were investigated. The HME tablets prepared from the powder blend containing both Eudragit((R)) RS PO and sodium bicarbonate exhibited sustained release properties and the tablets floated on the surface of the media for 24 h. The crosssectional morphology of the HME tablets showed a porous structure since CO2 gas was generated due to the thermal decomposition of sodium bicarbonate in the softened acrylic polymers at elevated temperature during the extrusion process. In contrast, all DC tablets prepared in this study showed no buoyancy and rapid drug release in the dissolution media. The drug release rate from floating HME tablets was controlled by both the incorporation of Eudragit((R)) E PO into the matrix tablet and the diameter of the die used in the extrusion equipment. The drug release profiles and buoyancy of the floating HME tablets were stable when stored at 40 degrees C/75%RH for 3 months. (c) 2006 Elsevier B.V. All rights reserved.